n=5;
a = 2 * ones(n,1);
a(n) = n;
C = ones(n);
nonz = 3*ones(n,1);
nonz(n) =n;
for i = 1:n-1
store(:,3*i-2:3*i)= [i i i+1
                     i i+1 i+1
                     1 -1  1];
                     end;
store(:, 3*(n-1)+1: 3*(n-1)+n) = [1:n; 1:n; ones(1,n)];
